Maximally recommended doses of angiotensin-converting enzyme (ACE) inhibitors do not completely prevent ACE-mediated formation of angiotensin II in chronic heart failure

Diverse biological functions of the renin-angiotensin system

The renin-angiotensin system (RAS) has been widely known as a circulating endocrine system involved in the control of blood pressure. However, components of RAS have been found to be localized in rather unexpected sites in the body including the kidneys, brain, bone marrow, immune cells, and reproductive system. These discoveries have led to steady, growing evidence of the existence of independent tissue RAS specific to several parts of the body. It is important to understand how RAS regulates these systems for a variety of reasons: It gives a better overall picture of human physiology, helps to understand and mitigate the unintended consequences of RAS-inhibiting or activating drugs, and sets the stage for potential new therapies for a variety of ailments. This review fulfills the need for an updated overview of knowledge about local tissue RAS in several bodily systems, including their components, functions, and medical implications.

The First Dedicated Comprehensive Heart Failure Program in the United States: The Division of Circulatory Physiology at Columbia Presbyterian (1992-2004)

The first dedicated multidisciplinary heart failure program in the United States was founded as the Division of Circulatory Physiology at the Columbia University College of Physicians & Surgeons in 1992. The Division was administratively and financially independent of the Division of Cardiology and grew to 24 faculty members at its peak. Its administrative innovations included (1) a comprehensive full-integrated service line, with 2 differentiated clinical teams, one devoted to drug therapy and the other to heart transplantation and ventricular assist devices; (2) a nurse specialist/physician assistant-led clinical service; and (3) a financial structure independent of (and not supported by) other cardiovascular medical or surgical services. The division had 3 overarching missions: (1) to promote a unique career development path for each faculty member to be linked to recognition in a specific area of heart failure expertise; (2) to change the trajectory and enhance the richness of intellectual discourse in the discipline of heart failure, so as to foster an understanding of fundamental mechanisms and to develop new therapeutics; and (3) to provide optimal medical care to patients and to promote the ability of other physicians to provide optimal care. The major research achievements of the division included (1) the development of beta-blockers for heart failure, from initial hemodynamic assessments to proof-of-concept studies to large-scale international trials; (2) the development and definitive assessment of flosequinan, amlodipine, and endothelin antagonists; (3) initial clinical trials and concerns with nesiritide; (4) large-scale trials evaluating dosing of angiotensin converting-enzyme inhibitors and the efficacy and safety of neprilysin inhibition; (5) identification of key mechanisms in heart failure, including neurohormonal activation, microcirculatory endothelial dysfunction, deficiencies in peripheral vasodilator pathways, noncardiac factors in driving dyspnea, and the first identification of subphenotypes of heart failure and a preserved ejection fraction; (6) the development of a volumetric approach to the assessment of myocardial shortening; (7) conceptualization and early studies of cardiac contractility modulation as a treatment for heart failure; (8) novel approaches to the identification of cardiac allograft rejection and new therapeutics to prevent allograft vasculopathy; and (9) demonstration of the effect of left ventricular assist devices to induce reverse remodeling, and the first randomized trial showing a survival benefit with ventricular assist devices. Above all, the division served as an exceptional incubator for a generation of leaders in the field of heart failure.

MasR and pGCA receptor activation protects primary vascular smooth muscle cells and endothelial cells against oxidative stress via inhibition of intracellular calcium

Cardiovascular diseases (CVDs) are associated with vascular smooth muscle cell (VSMC) and endothelial cell (EC) damage. Angiotensin1-7 (Ang1-7) and B-type natriuretic peptide (BNP) are responsible for vasodilation and regulation of blood flow. These protective effects of BNP are primarily mediated by the activation of sGCs/cGMP/cGKI pathway. Conversely, Ang1-7 inhibits Angiotensin II-induced contraction and oxidative stress via Mas receptor activation. Thus, the aim of the study was to determine the effect of co-activation of MasR and particulate guanylate cyclase receptor (pGCA) pathways by synthesized novel peptide (NP) in oxidative stress-induced VSMCs and ECs. MTT and Griess reagent assay kits were used for the standardization of the oxidative stress (H₂ O₂ ) induced model in VSMCs. The expression of targeted receptors in VSMC was done by RT-PCR and Western blot analysis. Protective effect of NP in VSMC and EC was determined by immunocytochemistry, FACS analysis, and Western blot analysis. Underlying mechanisms of EC-dependent VSMC relaxation were done by determining downstream mRNA gene expression and intracellular calcium imaging of cells. Synthesized NP significantly improved oxidative stress-induced injury in VSMCs. Remarkably, the actions of NP were superior to that of the Ang1-7 and BNP alone. Further, a mechanistic study in VSMC and EC suggested the involvement of upstream mediators of calcium inhibition for the therapeutic effect. NP is reported to possess vascular protective activities and is also involved in the improvement of endothelial damage. Moreover, it is highly effective than that of individual peptides BNP and Ang1-7 and therefore it may represent a promising strategy for CVDs.

Recent Developments in Drug Targets and Combination Therapy for the Clinical Management of Hypertension

Raised blood pressure is the most common complication worldwide that may lead to atherosclerosis and ischemic heart disease. Unhealthy lifestyles, smoking, alcohol consumption, junk food, and genetic disorders are some of the causes of hypertension. To treat this condition, numerous antihypertensive medications are available, either alone or in combination, that work via various mechanisms of action. Combinational therapy provides a certain advantage over monotherapy in the sense that it acts in multi mechanism mode and minimal drug amount is required to elicit the desired therapeutic effect. Such therapy is given to patients with systolic blood pressure greater than 20 mmHg and/or diastolic blood pressure exceeding 10 mmHg beyond the normal range, as well as those suffering from severe cardiovascular disease. The selection of antihypertensive medications, such as calcium channel blockers, angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), and low-dose diuretics, hinges on their ability to manage blood pressure effectively and reduce cardiovascular disease risks. This review provides insights into the diverse monotherapy and combination therapy approaches used for elevated blood pressure management. In addition, it offers an analysis of combination therapy versus monotherapy and discusses the current status of these therapies, from researchbased findings to clinical trials.

Impact of angiotensin-converting enzyme inhibition on hemodynamic and autonomic profile of elastase-2 knockout mice

Elastase-2 (ELA-2) is an angiotensin II-generating enzyme that participates in the cardiovascular system. ELA-2 is involved in hemodynamic and autonomic control and is upregulated in myocardial infarction and hypertension. The inhibition of angiotensin-converting enzyme (ACE) increased ELA-2 expression in the carotid arteries and heart of spontaneously hypertensive rats. In this study, we sought to investigate the role of ACE inhibition in hemodynamic and autonomic balance in elastase-2 knockout (ELA-2 KO) mice. Male ELA-2 KO and C57BL/6 mice were treated with the ACE inhibitor enalapril or saline for 10 days. After treatment, mice underwent surgery for cannulation of the femoral artery and arterial pressure recordings were made five days later in awake animals. The variability of systolic blood pressure (SBP) and pulse interval (PI) was evaluated in the time and frequency domain. Spontaneous baroreflex was assessed by the sequencing method. ACE inhibition caused a significant decrease in mean arterial pressure (117±2.2 vs 100±2.8 mmHg) and an increase in heart rate (570±32 vs 655±15 bpm) in ELA-2 KO mice. Despite a tendency towards reduction in the overall heart rate variability (standard deviation of successive values: 7.6±1.1 vs 4.7±0.6 ms, P=0.08), no changes were found in the root of the mean sum of squares or in the power of the high-frequency band. ACE inhibition did not change the spontaneous baroreflex indices (gain and baroreflex effectiveness index) in ELA-2 KO mice. Altogether, this data suggested that ACE played a role in the maintenance of hemodynamic function in ELA-2 KO mice.

Intratubular, Intracellular, and Mitochondrial Angiotensin II/AT1 (AT1a) Receptor/NHE3 Signaling Plays a Critical Role in Angiotensin II-Induced Hypertension and Kidney Injury

Hypertension is well recognized to be the most important risk factor for cardiovascular diseases, stroke, and end-stage kidney failure. A quarter of the world’s adult populations and 46% of the US adults develop hypertension and currently require antihypertensive treatments. Only 50% of hypertensive patients are responsive to current antihypertensive drugs, whereas remaining patients may continue to develop cardiovascular, stroke, and kidney diseases. The mechanisms underlying the poorly controlled hypertension remain incompletely understood. Recently, we have focused our efforts to uncover additional renal mechanisms, pathways, and therapeutic targets of poorly controlled hypertension and target organ injury using novel animal models or innovative experimental approaches. Specifically, we studied and elucidated the important roles of intratubular, intracellular, and mitochondrial angiotensin II (Ang II) system in the development of Ang II-dependent hypertension. The objectives of this invited article are to review and discuss our recent findings that (a) circulating and intratubular Ang II is taken up by the proximal tubules via the (AT₁) AT_1a receptor-dependent mechanism, (b) intracellular administration of Ang II in proximal tubule cells or adenovirus-mediated overexpression of an intracellular Ang II fusion protein selectively in the mitochonria of the proximal tubules induces blood pressure responses, and (c) genetic deletion of AT₁ (AT_1a) receptors or the Na⁺/H⁺ exchanger 3 selectively in the proximal tubules decreases basal blood pressure and attenuates Ang II-induced hypertension. These studies provide a new perspective into the important roles of the intratubular, intracellular, and mitochondrial angiotensin II/AT₁ (AT_1a) receptor signaling in Ang II-dependent hypertensive kidney diseases.

Evaluation of pathophysiological relationships between renin-angiotensin and ACE-ACE2 systems in cardiovascular disorders: from theory to routine clinical practice in patients with heart failure

Despite the progressive improvements in diagnosis and therapy during the first 20 years of this century, the morbidity and mortality of patients with heart failure (HF) remain high, resulting in an enormous health and economic burden. Only a further improvement in understanding the pathophysiological mechanisms related to the development of cardiac injury and dysfunction can allow more innovative and personalized approaches to HF management. The renin-angiotensin system (RAS) has a critical role in cardiovascular physiology by regulating blood pressure and electrolyte balance. The RAS is mainly regulated by both angiotensin converting enzyme (ACE) and type 2 angiotensin converting enzyme (ACE2). However, the balance between the various peptides and peptidases constituting the RAS/ACE pathway remains in great part unraveled in patients with HF. This review summarizes the role of the RAS/ACE axis in cardiac physiology and HF pathophysiology as well as some analytical issues relevant to the clinical and laboratory assessment of inter-relationships between these two systems. There is evidence that RAS peptides represent a dynamic network of peptides, which are altered in different HF states and influenced by medical therapy. However, the mechanisms of signal transduction have not been fully elucidated under physiological and pathophysiological conditions. Further investigations are necessary to explore novel molecular mechanisms related to the RAS, which will provide alternative therapeutic agents. Moreover, monitoring the circulating levels of active RAS peptides in HF patients may enable a personalized approach by facilitating assessment of the pathophysiological status of several cardiovascular diseases and thus better selection of therapies for HF patients.

Persistently Increased Systemic ACE2 Activity Is Associated With an Increased Inflammatory Response in Smokers With COVID-19

Background: Tobacco smoking is known to be involved in the pathogenesis of several cardiopulmonary diseases. Additionally, smokers are highly susceptible to infectious agents due to weakened immunity. However, the progression of lung injury based on SARS-CoV-2-mediated COVID-19 pathogenesis amongst smokers and those with pre-existing pulmonary diseases is not known. We determined the systemic levels and activity of COVID-19 associated proteins, cytokine/chemokines, and lipid mediators (lipidomics) amongst COVID-19 patients with and without a history of smoking to understand the underlying susceptible factor in the pathogenesis of COVID-19.

Methods: We obtained serum from healthy (CoV−), COVID-19 positive (CoV+), and COVID-19 recovered (CoV Rec) subjects with and without a history of smoking. We conducted a Luminex multiplex assay (cytokine levels), LC/MS (eicosanoids or oxylipin panel), and ACE2 enzymatic activity assays on the serum samples to determine the systemic changes in COVID-19 patients.

Results: On comparing the levels of serum ACE2 amongst COVID-19 (positive and recovered) patients and healthy controls, we found a pronounced increase in serum ACE2 levels in patients with COVID-19 infection. Furthermore, ACE2 enzyme activity was significantly increased amongst COVID-19 patients with a smoking history. Also, we analyzed the levels of Angiotensin 1–7 (Ang1–7) peptide, the product of enzymatic action of ACE2, in the serum samples. We found significantly high levels of Ang1–7 in the serum of both CoV+ and CoV Rec patients. Our data further demonstrated a smoking-induced increase in serum furin and inflammatory cytokine [IFN_γ(p = 0.0836), Eotaxin (p < 0.05), MCP-1 (p < 0.05), and IL-9 (p = 0.0991)] levels in COVID-19 patients as compared to non-smoking controls. Overall, our results show that smoking adversely affects the levels of systemic inflammatory markers and COVID-19 associated proteins, thus suggesting that COVID-19 infection may have severe outcomes amongst smokers.

Myocardial Angiotensin Metabolism in End-Stage Heart Failure

BACKGROUND

The myocardium exhibits an adaptive tissue-specific renin-angiotensin system (RAS), and local dysbalance may circumvent the desired effects of pharmacologic RAS inhibition, a mainstay of heart failure with reduced ejection fraction (HFrEF) therapy.

OBJECTIVES

This study sought to investigate human myocardial tissue RAS regulation of the failing heart in the light of current therapy.

METHODS

Fifty-two end-stage HFrEF patients undergoing heart transplantation (no RAS inhibitor: n = 9; angiotensin-converting enzyme [ACE] inhibitor: n = 28; angiotensin receptor blocker [ARB]: n = 8; angiotensin receptor neprilysin-inhibitor [ARNi]: n = 7) were enrolled. Myocardial angiotensin metabolites and enzymatic activities involved in the metabolism of the key angiotensin peptides angiotensin 1-8 (AngII) and Ang1-7 were determined in left ventricular samples by mass spectrometry. Circulating angiotensin concentrations were assessed for a subgroup of patients.

RESULTS

AngII and Ang2-8 (AngIII) were the dominant peptides in the failing heart, while other metabolites, especially Ang1-7, were below the detection limit. Patients receiving an ARB component (i.e., ARB or ARNi) had significantly higher levels of cardiac AngII and AngIII (AngII: 242 [interquartile range (IQR): 145.7 to 409.9] fmol/g vs 63.0 [IQR: 19.9 to 124.1] fmol/g; p < 0.001; and AngIII: 87.4 [IQR: 46.5 to 165.3] fmol/g vs 23.0 [IQR: <5.0 to 59.3] fmol/g; p = 0.002). Myocardial AngII concentrations were strongly related to circulating AngII levels. Myocardial RAS enzyme regulation was independent from the class of RAS inhibitor used, particularly, a comparable myocardial neprilysin activity was observed for patients with or without ARNi. Tissue chymase, but not ACE, is the main enzyme for cardiac AngII generation, whereas AngII is metabolized to Ang1-7 by prolyl carboxypeptidase but not to ACE2. There was no trace of cardiac ACE2 activity.

CONCLUSIONS

The failing heart contains considerable levels of classical RAS metabolites, whereas AngIII might be an unrecognized mediator of detrimental effects on cardiovascular structure. The results underline the importance of pharmacologic interventions reducing circulating AngII actions, yet offer room for cardiac tissue-specific RAS drugs aiming to limit myocardial AngII/AngIII peptide accumulation and actions.

Effect of Traditional Chinese Medicine Poge Heart-Saving Decoction on Cardiac Function in Heart Failure Rat Model

Background

Poge heart-saving decoction (PHSD) has been used as a medicine treating heart failure in China for many years. The study aimed to explore the effect of PHSD on cardiac function in heart failure conditions and its underlying mechanism.

Methods

Adriamycin was used to induce the model of heart failure (HF) in rats. Sixty rats were randomly divided into six groups: blank control group, sham group, 9.33 g/kg group (low-PHSD, test group), 13.995 g/kg group (moderate-PHSD, test group), 18.66 g/kg group (high-PHSD, test group), and fosinopril group (4.67 mg/kg, comparison test group). Cardiac ultrasound was used to evaluate the cardiac function of the rats, and radioimmunoassay was used to measure aldosterone (ALD) and angiotensin II (AngII) levels in the serum.

Results

Compared with the blank control group, the left ventricular end-diastolic dimension (LVEDd) and left ventricular end-systolic dimension (LVEDs) in the sham group were increased (1.04 ± 0.12 vs. 0.67 ± 0.13 cm; 0.75 ± 0.13 vs. 0.28 ± 0.10 cm; P < 0.05), and the left ventricular ejection fraction was decreased (36.65 ± 5.74 vs. 76.09 ± 4.23%; P < 0.05). The ejection fraction of HF rats was increased in 9.33 g/kg group, 13.995 g/kg group, and 18.66 g/kg group compared with those of the sham group (57.13 ± 1.63, 58.43 ± 1.98, and 59.21 ± 1.37 vs. 36.65 ± 5.74%; P < 0.05). PHSD also improved cardiac function by reducing the LVEDd and LVEDs (0.88 ± 0.11, 0.75 ± 0.13, and 0.72 ± 0.18 vs. 1.04 ± 0.12 cm; 0.62 ± 0.10, 0.63 ± 0.17, and 0.45 ± 0.11 vs. 0.75 ± 0.13 cm; P < 0.05). The levels of ALD and AngII in the serum of rats in the sham group were significantly higher than those in the blank control group (371.58 ± 39.25 vs. 237.12 ± 17.35 μg/L; 232.18 ± 16.33 vs. 159.44 ± 18.42 pg/L; P < 0.05). The ALD and AngII of the rats in all of the three PHSD groups and the fosinopril group were decreased (276.81 ± 25.63, 277.18 ± 21.35, 268.19 ± 19.28, and 271.47 ± 28.96 vs. 371.58 ± 39.25 μg/L; 169.41 ± 27.53, 168.81 ± 19.78, 164.23 ± 21.34, and 174.27 ± 22.84 vs. 232.18 ± 16.33 pg/L; P < 0.05). The histopathological changes of the myocardium in the sham group showed the disorganized fiber, shaded staining, fracture, and zonation. The fracture of the myocardium was relieved in all groups except the sham group and the blank control group.

Conclusion

Therefore, PHSD could shorten LVEDd and LVEDs of rats and reverse ventricular remodeling. The mechanism might be related to the inhibition of the activation level of renin-angiotensin-aldosterone system (especially ALD and AngII) and decreasing the postload of the heart.

Sex Differences in the Renal Vascular Responses of AT1 and Mas Receptors in Two-Kidney-One-Clip Hypertension

Background

The prevalence and severity of hypertension, as well as the activity of the systemic and local renin angiotensin systems (RASs), are gender related, with more symptoms in males than in females. However, the underlying mechanisms are not well understood. In this study, we investigated sex differences in renal vascular responses to angiotensin II (Ang II) administration with and without Ang II type 1 and Mas receptor (AT₁R and MasR) antagonists (losartan and A779) in the 2K1C rat model of renovascular hypertension.

Methods

Male and female 2K1C rats were divided into 8 experimental groups (4 of each sex) treated with vehicle, losartan, A779, or A779+losartan. Responses of mean arterial pressure (MAP), renal blood flow (RBF), and renal vascular resistance (RVR) to Ang II were determined.

Results

In both sexes, the basal MAP, RBF, and RVR were not significantly different between the four groups during the control period. The Ang II administration decreased RBF and increased RVR in a dose-related manner in both sexes pretreated with vehicle or A779 (P_dose < 0.0001), but in vehicle pretreated groups, RBF and RVR responses were different between male and female rats (P_group < 0.05). AT₁R blockade increased RBF and decreased RVR responses to Ang II, and no difference between the sexes was detected. Coblockades of AT₁R and MasR receptors increased RBF response to Ang II significantly in males alone but not in females (P_group=0.04).

Conclusion

The impact of Ang II on RBF and RVR responses seems to be gender related with a greater effect on males, and this sex difference abolishes by Mas receptor blockade. However, the paradoxical role of dual losartan and A779 may provide the different receptor interaction in RAS between male and female rats.

Novel therapeutics for the treatment of hypertension and its associated complications: peptide- and nonpeptide-based strategies

The renin-angiotensin-aldosterone system (RAAS) is responsible for maintaining blood pressure and vascular tone. Modulation of the RAAS, therefore, interferes with essential cellular processes and leads to high blood pressure, oxidative stress, inflammation, fibrosis, and hypertrophy. Consequently, these conditions cause fatal cardiovascular and renal complications. Thus, the primary purpose of hypertension treatment is to diminish or inhibit overactivated RAAS. Currently available RAAS inhibitors have proven effective in reducing blood pressure; however, beyond hypertension, they have failed to treat end-target organ injury. In addition, RAAS inhibitors have some intolerable adverse effects, such as hyperkalemia and hypotension. These gaps in the available treatment for hypertension require further investigation of the development of safe and effective therapies. Current research is focused on the combination of existing and novel treatments that neutralize the angiotensin II type I (AT1) receptor-mediated action of the angiotensin II peptide. Preclinical studies of peptide- and nonpeptide-based therapeutic agents demonstrate their conspicuous impact on the treatment of cardiovascular diseases in animal models. In this review, we will discuss novel therapeutic agents being developed as RAAS inhibitors that show prominent effects in both preclinical and clinical studies. In addition, we will also highlight the need for improvement in the efficacy of existing drugs in the absence of new prominent antihypertensive drugs.

Angiotensin converting enzyme 2 at the interface between renin-angiotensin system inhibition and coronavirus disease 2019

The coronavirus disease 2019 (COVID-19) is the third major coronavirus outbreak of this century. Its aetiological agent, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), requires angiotensin converting enzyme 2 (ACE2) for cellular entry. The commonly used angiotensin converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) could affect SARS-CoV-2 infectivity and may alter COVID-19 disease progression by altering ACE2 expression. Current evidence of ACEI/ARB-ACE2 interaction as well as the effects of ACEIs/ARBs on viral-associated acute lung injury is summarized and discussed in this review. This review assesses the evidence gathered so far and highlights the research that needs to be done to help inform clinical decision making.

The renin-angiotensin system: going beyond the classical paradigms

Thirty years ago, a novel axis of the renin-angiotensin system (RAS) was unveiled by the discovery of angiotensin-(1−7) [ANG-(1−7)] generation in vivo. Later, angiotensin-converting enzyme 2 (ACE2) was shown to be the main mediator of this reaction, and Mas was found to be the receptor for the heptapeptide. The functional analysis of this novel axis of the RAS that followed its discovery revealed numerous protective actions in particular for cardiovascular diseases. In parallel, similar protective actions were also described for one of the two receptors of ANG II, the ANG II type 2 receptor (AT₂R), in contrast to the other, the ANG II type 1 receptor (AT₁R), which mediates deleterious actions of this peptide, e.g., in the setting of cardiovascular disease. Very recently, another branch of the RAS was discovered, based on angiotensin peptides in which the amino-terminal aspartate was replaced by alanine, the alatensins. Ala-ANG-(1−7) or alamandine was shown to interact with Mas-related G protein-coupled receptor D, and the first functional data indicated that this peptide also exerts protective effects in the cardiovascular system. This review summarizes the presentations given at the International Union of Physiological Sciences Congress in Rio de Janeiro, Brazil, in 2017, during the symposium entitled “The Renin-Angiotensin System: Going Beyond the Classical Paradigms,” in which the signaling and physiological actions of ANG-(1−7), ACE2, AT₂R, and alatensins were reported (with a focus on noncentral nervous system-related tissues) and the therapeutic opportunities based on these findings were discussed.

Insufficient hypothalamic angiotensin-converting enzyme 2 is associated with hypertension in SHR rats

Angiotensin-Converting Enzyme 2 (ACE2) is a key enzyme in the renin-angiotensin system (RAS), which is implicated in the pathogenesis of hypertension and other cardiovascular diseases. In this study we investigated the expression of ACE2 in the hypothalamus and pituitary tissues and its relationship to hypertension by comparing them in male WKY and SHR rats. We observed that the plasma levels of corticotrophin releasing hormone (CRH), adrenocorticotropic hormone (ACTH) and aldosterone (ALD) were all lower in SHR than WKY rats (P<0.05), whereas plasma angiotensin II (AngII) levels were higher in SHR rats (P<0.05). Levels of ACE mRNA and protein were higher in the hypothalamus of SHR than WKY rats (P<0.05). By contrast, hypothalamic expression of ACE2 protein was lower in SHR rats (P<0.05), despite comparable mRNA levels in SHR and WKY rats. There were no differences in the expression levels of ACE, ACE2, AT1 or Mas mRNA in the pituitaries of SHR and WKY rats (P>0.05). These results suggest that insufficiency of hypothalamic ACE2 is associated with hypertension in SHR rats.

Roles of Angiotensin Peptides and Recombinant Human ACE2 in Heart Failure

BACKGROUND

The renin-angiotensin system (RAS) is activated in heart failure (HF) and inhibition of RAS is a mainstay therapy for HF. Angiotensin-converting enzyme 2 (ACE2) and its product, angiotensin 1-7 (Ang-[1-7]), are important negative regulators of the RAS.

OBJECTIVES

A comprehensive examination of angiotensin peptide levels and therapeutic effects of recombinant human ACE2 (rhACE2) on peptide metabolism was evaluated in human plasma and explanted heart tissue from patients with HF.

METHODS

Using prospective cohorts with chronic (n = 59) and acute (n = 42) HF, plasma angiotensin analysis was performed using a unique liquid chromatography-mass spectrometry/mass spectroscopy method quantifying circulating and equilibrium levels. Angiotensin II (Ang II) metabolism was examined in human explanted hearts with dilated cardiomyopathy (n = 25).

RESULTS

The dynamic range of the RAS was large, with equilibrium angiotensin levels being 8- to 10-fold higher compared with circulating angiotensin levels. In chronic HF patients receiving ACE inhibition, plasma Ang II was suppressed and plasma Ang-(1-7) was elevated, whereas acute HF and patients receiving angiotensin receptor blocker had higher plasma Ang II with lower Ang-(1-7) levels. Suppressed Ang-(1-7)/Ang II ratio was associated with worsening HF symptoms and longer hospitalization. Recombinant human ACE2 effectively metabolized Ang-(1-10) and Ang II into Ang-(1-9) and Ang-(1-7), respectively. Myocardial Ang II levels in explanted human hearts with dilated cardiomyopathy were elevated despite ACE inhibition with elevated chymase activity, and Ang II was effectively converted to Ang-(1-7) by rhACE2.

CONCLUSIONS

Plasma angiotensin peptides represent a dynamic network that is altered in HF and in response to rhACE2. An increased plasma Ang-(1-7) level is linked to ACE inhibitor use, whereas acute HF reduced Ang-(1-7) levels and suppressed the Ang-(1-7)/Ang II ratio. Increased chymase activity elevated Ang II levels in failing human hearts. Use of rhACE2 effectively normalized elevated Ang II while increasing Ang-(1-7) and Ang-(1-9) levels.

Importance of endogenous compensatory vasoactive peptides in broadening the effects of inhibitors of the renin-angiotensin system for the treatment of heart failure

The magnitude of the clinical benefits produced by inhibitors of the renin-angiotensin system in heart failure has been modest, possibly because of the ability of renin-angiotensin activity to escape from suppression during long-term treatment. Efforts to intensify pharmacological blockade by use of dual inhibitors that interfere with the renin-angiotensin system at multiple sites have not yielded consistent incremental clinical benefits, but have been associated with serious adverse reactions. By contrast, potentiation of endogenous compensatory vasoactive peptides can act to enhance the survival effects of inhibitors of the renin-angiotensin system, as evidenced by trials that have compared angiotensin-converting enzyme inhibitors with drugs that inhibit both the renin-angiotensin system and neprilysin. Several endogenous vasoactive peptides act as adaptive mechanisms, and their augmentation could help to broaden the benefits of renin-angiotensin system inhibitors for patients with heart failure.

Elastase-2, a Tissue Alternative Pathway for Angiotensin II Generation, Plays a Role in Circulatory Sympathovagal Balance in Mice

In vitro and ex vivo experiments indicate that elastase-2 (ELA-2), a chymotrypsin-serine protease elastase family member 2A, is an alternative pathway for angiotensin II (Ang II) generation. However, the role played by ELA-2 in vivo is unclear. We examined ELA-2 knockout (ELA-2KO) mice compared to wild-type (WT) mice and determined whether ELA-2 played a role in hemodynamics [arterial pressure (AP) and heart rate (HR)], cardiocirculatory sympathovagal balance and baroreflex sensitivity. The variability of systolic arterial pressure (SAP) and pulse interval (PI) for evaluating autonomic modulation was examined for time and frequency domains (spectral analysis), whereas a symbolic analysis was also used to evaluate PI variability. In addition, baroreflex sensitivity was examined using the sequence method. Cardiac function was evaluated echocardiographically under anesthesia. The AP was normal whereas the HR was reduced in ELA-2KO mice (425 ± 17 vs. 512 ± 13 bpm from WT). SAP variability and baroreflex sensitivity were similar in both strains. The LF power from the PI spectrum (33.6 ± 5 vs. 51.8 ± 4.8 nu from WT) and the LF/HF ratio (0.60 ± 0.1 vs. 1.45 ± 0.3 from WT) were reduced, whereas the HF power was increased (66.4 ± 5 vs. 48.2 ± 4.8 nu from WT) in ELA-2KO mice, indicating a shift toward parasympathetic modulation of HR. Echocardiographic examination showed normal fractional shortening and an ejection fraction in ELA-2KO mice; however, the cardiac output, stroke volume, and ventricular size were reduced. These findings provide the first evidence that ELA-2 acts on the sympathovagal balance of the heart, as expressed by the reduced sympathetic modulation of HR in ELA-2KO mice.

Elastase-2, an angiotensin II-generating enzyme, contributes to increased angiotensin II in resistance arteries of mice with myocardial infarction

BACKGROUND AND PURPOSE

Angiotensin II (Ang II), whose generation largely depends on angiotensin-converting enzyme (ACE) activity, mediates most of the renin-angiotensin-system (RAS) effects. Elastase-2 (ELA-2), a chymotrypsin-serine protease elastase family member 2A, alternatively generates Ang II in rat arteries. Myocardial infarction (MI) leads to intense RAS activation, but mechanisms involved in Ang II-generation in resistance arteries are unknown. We hypothesized that ELA-2 contributes to vascular Ang II generation and cardiac damage in mice subjected to MI.

EXPERIMENTAL APPROACH

Concentration-effect curves to Ang I and Ang II were performed in mesenteric resistance arteries from male wild type (WT) and ELA-2 knockout (ELA-2KO) mice subjected to left anterior descending coronary artery ligation (MI).

KEY RESULTS

MI size was similar in WT and ELA-2KO mice. Ejection fraction and fractional shortening after MI similarly decreased in both strains. However, MI decreased stroke volume and cardiac output in WT, but not in ELA-2KO mice. Ang I-induced contractions increased in WT mice subjected to MI (MI-WT) compared with sham-WT mice. No differences were observed in Ang I reactivity between arteries from ELA-2KO and ELA-2KO subjected to MI (MI-ELA-2KO). Ang I contractions increased in arteries from MI-WT versus MI-ELA-2KO mice. Chymostatin attenuated Ang I-induced vascular contractions in WT mice, but did not affect Ang I responses in ELA-2KO arteries.

CONCLUSIONS AND IMPLICATIONS

These results provide the first evidence that ELA-2 contributes to increased Ang II formation in resistance arteries and modulates cardiac function after MI, implicating ELA-2 as a key player in ACE-independent dysregulation of the RAS.

Role of the ACE2/Angiotensin 1-7 Axis of the Renin-Angiotensin System in Heart Failure

Heart failure (HF) remains the most common cause of death and disability, and a major economic burden, in industrialized nations. Physiological, pharmacological, and clinical studies have demonstrated that activation of the renin-angiotensin system is a key mediator of HF progression. Angiotensin-converting enzyme 2 (ACE2), a homolog of ACE, is a monocarboxypeptidase that converts angiotensin II into angiotensin 1-7 (Ang 1-7) which, by virtue of its actions on the Mas receptor, opposes the molecular and cellular effects of angiotensin II. ACE2 is widely expressed in cardiomyocytes, cardiofibroblasts, and coronary endothelial cells. Recent preclinical translational studies confirmed a critical counter-regulatory role of ACE2/Ang 1-7 axis on the activated renin-angiotensin system that results in HF with preserved ejection fraction. Although loss of ACE2 enhances susceptibility to HF, increasing ACE2 level prevents and reverses the HF phenotype. ACE2 and Ang 1-7 have emerged as a key protective pathway against HF with reduced and preserved ejection fraction. Recombinant human ACE2 has been tested in phase I and II clinical trials without adverse effects while lowering and increasing plasma angiotensin II and Ang 1-7 levels, respectively. This review discusses the transcriptional and post-transcriptional regulation of ACE2 and the role of the ACE2/Ang 1-7 axis in cardiac physiology and in the pathophysiology of HF. The pharmacological and therapeutic potential of enhancing ACE2/Ang 1-7 action as a novel therapy for HF is highlighted.

Comparison of high- versus low-tissue affinity ACE-inhibitor treatment on circulating aldosterone levels in patients with chronic heart failure

Introduction. Previous animal studies of chronic heart failure (CHF) suggest that angiotensin-converting enzyme (ACE) inhibitors of differing tissue avidity provide varying levels of renin-angiotensin system (RAS) suppression. Human studies have not consistently confirmed these animal findings. We hypothesised that production of circulating aldosterone (ALDO) would be suppressed to a greater extent in subjects treated with an ACE-inhibitor of higher tissue avidity. We randomised subjects with stable CHF to receive the low-tissue affinity ACE-inhibitor enalapril (ENAL) or the high-tissue affinity ACE-inhibitor trandolapril (TRAN), and assessed circulating ALDO levels at baseline and after eight weeks of treatment.

Methods. Thirty clinically stable subjects with CHF and left ventricular ejection fraction (LVEF ) < 40% who were in a steady-state fluid balance were enrolled into a prospective, randomised double-blind trial. After a one month run-in period for standardisation to initial ACE-inhibition with ENAL, baseline circulating ALDO levels were measured and patients were randomised to receive ENAL 40 mg versus O TRAN 4 mg (or the maximally tolerated doses) for eight weeks. Final determination of ALDO levels were made at the end of the 8-week study period.

Results. Baseline clinical characteristics including age, diabetes, LVEF, serum sodium, potassium and creatinine concentrations, and background medications were similar in both groups. We found no statistically significant difference in circulating ALDO levels between the ENAL and TRAN groups at the end of the 8-week study period. [ENAL (12.6 vs. 13.3 ng/dL);TRAN (12.5 vs. 14.5 ng/dL);p=NS].

Conclusion. We found no statistically significant difference in circulating ALDO levels between high- and low-tissue affinity ACE-inhibitor therapy. Further studies assessing ALDO production at the tissue level is warranted.

Interaction of -blockers and angiotensin receptor blockers/ACE inhibitors in heart failure

The renin-angiotensin-aldosterone system contributes to the progression of heart failure and its inhibition slows ventricular remodelling and favourably affects morbidity and mortality. -blockers exert a remarkably favourable effect on progression that may be mediated at least in part by renin inhibition. Although earlier trials suggested a possible adverse interaction when an angiotensin receptor blocker was added to an angiotensin-converting enzyme inhibitor and a -blocker, a recent study and newly analysed mechanistic data indicate that the triple combination provides modest additional inhibition of angiotensin that can further slow progression of disease.

Complete inhibition of the renin-angiotensin-aldosterone system; where do we stand?

PURPOSE OF REVIEW

This review presents the role of combination therapy of renin-angiotensin-aldosterone system blockade on cardiovascular and kidney disease.

RECENT FINDINGS

Three large randomized controlled trials comparing combination therapy of renin-angiotensin-aldosterone system blockade to monotherapy in individuals with increased cardiovascular risk, chronic kidney disease, or diabetic nephropathy have been reported. These trials - ONTARGET, ALTITUDE, and VA NEPHRON-D - demonstrated an excess risk of adverse effects [especially acute kidney injury (AKI) and hyperkalemia] with combination therapy, without significant benefit in reducing cardiovascular and renal morbidity.

SUMMARY

Current evidence supports avoiding dual renin-angiotensin-aldosterone system blockade in patients with chronic kidney disease. Subsequent studies of dual renin-angiotensin-aldosterone system blockade should examine adverse event risks and renal progression endpoints.

Renin-angiotensin system phenotyping as a guidance toward personalized medicine for ACE inhibitors: can the response to ACE inhibition be predicted on the basis of plasma renin or ACE?

PURPOSE & METHODS

Not all hypertensive patients respond well to ACE inhibition. Here we determined whether renin-angiotensin system (RAS) phenotyping, i.e., the measurement of renin or ACE, can predict the individual response to RAS blockade, either chronically (enalapril vs. enalapril + candesartan) or acutely (enalapril ± hydrochlorothiazide, HCT).

RESULTS

Chronic enalapril + candesartan induced larger renin rises, but did not lower blood pressure (BP) more than enalapril. Similar observations were made for enalapril + HCT vs. enalapril when given acutely. Baseline renin predicted the peak changes in BP chronically, but not acutely. Baseline ACE levels had no predictive value. Yet, after acute drug intake, the degree of ACE inhibition, like Δrenin, did correlate with ΔBP. Only the relationship with Δrenin remained significant after chronic RAS blockade. Thus, a high degree of ACE inhibition and a steep renin rise associate with larger acute responses to enalapril. However, variation was large, ranging >50 mm Hg for a given degree of ACE inhibition or Δrenin. The same was true for the relationships between Δrenin and ΔBP, and between baseline renin and the maximum reduction in BP in the chronic study.

CONCLUSIONS

Our data do not support that RAS phenotyping will help to predict the individual BP response to RAS blockade. Notably, these conclusions were reached in a carefully characterized, homogenous population, and when taking into account the known fluctuations in renin that relate to gender, age, ethnicity, salt intake and diuretic treatment, it seems unlikely that a cut-off renin level can be defined that has predictive value.

Drug Interactions in Parkinson's Disease: Safety of Pharmacotherapy for Arterial Hypertension

BACKGROUND

Parkinson's disease (PD) is a progressive neurodegenerative disorder of the central nervous system, observed in patients aged older than 50 years. In this study, we review interactions between therapies used in PD and selected antihypertensive agents. Moreover, in view of the lack of evidence-based recommendations regarding the pharmacotherapy of arterial hypertension in PD patients, we propose effective and safe therapeutic algorithms for these two coexisting conditions.

METHOD

We used the "Drug interactions" database affiliated with the Ministry of Health, which allows for the identification of interactions between compared active compounds. The database is updated on a monthly basis and all data are consistent with current legislation. For information about interactions, we additionally added data from the British National Formulary, a joint publication of the British Medical Association and the Royal Pharmaceutical Society of Great Britain. In this analysis, we also used data from Micromedex^®, Cerner Multum™, Wolters Kluwer™, Lexicomp^® and Stockley's^®. We analysed the potential interactions between antihypertensive and anti-parkinsonian agents included in respective guidelines on the pharmacotherapy of these conditions.

RESULTS

Our analysis revealed the lack of clinically relevant interactions between preparations of levodopa and benserazide (used for the treatment of PD) and angiotensin-converting enzyme inhibitors, antagonists of AT₁ receptor for angiotensin II or antagonists of β-adrenoreceptors (β-adrenolytics).

CONCLUSION

To avoid major drug-to-drug interactions, patients receiving preparations of levodopa and benserazide should be prescribed angiotensin-converting enzyme inhibitors, antagonists of AT₁ receptor for angiotensin II, or antagonists of β-adrenoreceptors (β-adrenolytics) as the first-line agents of antihypertensive treatment.

Ang (1-7) is a modulator of the vasoconstrictor actions of Ang I and Ang II

INTRODUCTION

The role of angiotensin (Ang) (1-7) on the vasoconstrictor effect induced by angiotensins could be different in the presence of an ACE inhibitor or an ARB because Ang II is formed through several pathways. Therefore, the role of Ang (1-7) in Ang I and Ang II contraction was evaluated in aortas from Wistar rats after 48-hour coronary occlusion treated with captopril or losartan.

METHODS

Concentration-response curves to Ang I or Ang II were conducted in the absence or presence of Ang (1-7) and A779: a) sham group; b) 48-hour coronary occlusion; c) treated with captopril or d) losartan (3.1 mg/kg, i.m.).

RESULTS

Captopril caused a significant increase in the contractile effect of Ang I and Ang II, while losartan reduced it. The presence of Ang (1-7) in the captopril group showed a reduction of the contraction compared to the sham group, while the treatment with losartan did not show a significant difference. Ang (1-7) presents effects different from Ang I or Ang II.

CONCLUSION

Ang (1-7) showed a modulatory role, suggesting Ang I did as well after treatment with an ACE inhibitor but not with an AT1 receptor antagonist.

Aldosterone breakthrough with benazepril in furosemide-activated renin-angiotensin-aldosterone system in normal dogs

Pilot studies in our laboratory revealed that furosemide-induced renin-angiotensin-aldosterone system (RAAS) activation was not attenuated by the subsequent co-administration of benazepril. This study was designed to evaluate the effect of benazepril on angiotensin-converting enzyme (ACE) activity and furosemide-induced circulating RAAS activation. Our hypothesis was that benazepril suppression of ACE activity would not suppress furosemide-induced circulating RAAS activation, indicated by urinary aldosterone concentration. Ten healthy hound dogs were used in this study. The effect of furosemide (2 mg/kg p.o., q12h; Group F; n = 5) and furosemide plus benazepril (1 mg/kg p.o., q24h; Group FB; n = 5) on circulating RAAS was determined by plasma ACE activity, 4-6 h posttreatment, and urinary aldosterone to creatinine ratio (UAldo:C) on days -1, -2, 1, 3, and 7. There was a significant increase in the average UAldo:C (μg/g) after the administration of furosemide (Group F baseline [average of days -1 and -2] UAldo:C = 0.41, SD 0.15; day 1 UAldo:C = 1.1, SD 0.56; day 3 UAldo:C = 0.85, SD 0.50; day 7 UAldo:C = 1.1, SD 0.80, P < 0.05). Benazepril suppressed ACE activity (U/L) in Group FB (Group FB baseline ACE = 16.4, SD 4.2; day 1 ACE = 3.5, SD 1.4; day 3 ACE = 1.6, SD 1.3; day 7 ACE = 1.4, SD 1.4, P < 0.05) but did not significantly reduce aldosterone excretion (Group FB baseline UAldo:C = 0.35, SD 0.16; day 1 UAldo:C = 0.79, SD 0.39; day 3 UAldo:C 0.92, SD 0.48, day 7 UAldo:C = 0.99, SD 0.48, P < 0.05). Benazepril decreased plasma ACE activity but did not prevent furosemide-induced RAAS activation, indicating aldosterone breakthrough (escape). This is particularly noteworthy in that breakthrough is observed at the time of initiation of RAAS suppression, as opposed to developing after months of therapy.

The evolving landscape of RAAS inhibition: from ACE inhibitors to ARBs, to DRIs and beyond

Chronic renin-angiotensin-aldosterone system (RAAS) activation has far-reaching effects on cardiometabolic risk and is a substantial contributor to cardiovascular (CV) disease and renal dysfunction. The vascular effects of sustained RAAS activation are associated with hemodynamic imbalances, as well as inflammatory stimulation and prothrombotic processes that lead to fibrosis, endothelial dysfunction and cellular remodeling. RAAS inhibition therapies, which include the use of angiotensin-converting enzyme inhibitors, angiotensin receptor blockers and more recently, direct renin inhibitors, have been used in clinical practice for more than 30 years. Our understanding of how these drugs work, alone and in combination, has contributed to an expanding landscape of treatment options and established RAAS inhibition as essential for reducing the risk of CV and renal disease. This perspective provides a historical overview of how RAAS inhibitors have evolved to their present-day status and will discuss recently discovered functions for components of this complicated and powerful regulatory system.

Reactive oxygen species-targeted therapeutic interventions for atrial fibrillation

Atrial fibrillation (AF) is the most common arrhythmia that requires medical attention, and its incidence is increasing. Current ion channel blockade therapies and catheter ablation have significant limitations in treatment of AF, mainly because they do not address the underlying pathophysiology of the disease. Oxidative stress has been implicated as a major underlying pathology that promotes AF; however, conventional antioxidants have not shown impressive therapeutic effects. A more careful design of antioxidant therapies and better selection of patients likely are required to treat effectively AF with antioxidant agents. Current evidence suggest inhibition of prominent cardiac sources of reactive oxygen species (ROS) such as nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and targeting subcellular compartments with the highest levels of ROS may prove to be effective therapies for AF. Increased serum markers of oxidative stress may be an important guide in selecting the AF patients who will most likely respond to antioxidant therapy.

Failure to intensify hypertension therapy after rejected aliskiren claims

BACKGROUND

Failure to intensify therapy when indicated is a serious problem in the management of hypertension. Patients having an antihypertensive prescription rejected because of utilization management tools may be at a high risk of failing to intensify their therapy when it is warranted.

OBJECTIVE

The goal of this study was to investigate the patterns of therapy change after rejected aliskiren claims because of utilization management tools such as prior authorization, step therapy, and restrictive formulary.

METHODS

A retrospective study was conducted using data from a large national pharmacy benefits manager. Patients with a rejected aliskiren claim because of utilization management and who were naive to aliskiren treatment before having a rejected aliskiren claim were included. Patients were followed up for 6 months after the initial rejected aliskiren claim to see whether there was a therapy change. Therapy change was defined as titration of old regimens, fulfillment of aliskiren, or fulfillment of a new antihypertensive medication not used previously.

RESULTS

A total of 1955 patients were identified (mean age, 64.5 years; 54.4% female). Six months after having rejected aliskiren claims, 36.8% overcame the utilization management and filled aliskiren; 45.1% filled a new antihypertensive medication not used previously; and 10.8% patients titrated old antihypertensive medications. More than one quarter of patients (28.4%) had no change in their antihypertensive treatment. Logistic regression analysis revealed that patients rejected because of prior authorization (odds ratio = 4.00 [95% CI, 1.89-8.44]) or step therapy (odds ratio = 2.59 [95% CI, 1.26-5.32]) were more likely to have a therapy change compared with patients rejected because of a restrictive formulary.

CONCLUSIONS

A significant number of patients had no therapy change 6 months after having rejected aliskiren claims because of utilization management tools, indicating potential clinical inertia or lack of therapy intensification in hypertension management. Patients with restrictive formularies were least likely to have a therapy change. More aggressive follow-up with patients with a rejected claim may be warranted to reduce treatment gaps.

Role of the renin-angiotensin system in the pathogenesis of intimal hyperplasia: therapeutic potential for prevention of vein graft failure?

The saphenous vein remains the most widely used conduit for peripheral and coronary revascularization despite a high rate of vein graft failure. The most common cause of vein graft failure is intimal hyperplasia. No agents have been proven to be successful for the prevention of intimal hyperplasia in human subjects. The renin-angiotensin system is essential in the regulation of vascular tone and blood pressure in physiologic conditions. However, this system mediates cardiovascular remodeling in pathophysiologic states. Angiotensin II is becoming increasingly recognized as a potential mediator of intimal hyperplasia. Drugs modulating the renin-angiotensin system include angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. These drugs are powerful inhibitors of atherosclerosis and cardiovascular remodeling, and they are first-line agents for management of several medical conditions based on class I evidence that they delay progression of cardiovascular disease and improve survival. Several experimental models have demonstrated that these agents are capable of inhibiting intimal hyperplasia. However, there are no data supporting their role in prevention of intimal hyperplasia in patients with vein grafts. This review summarizes the physiology of the renin-angiotensin system, the role of angiotensin II in the pathogenesis of cardiovascular remodeling, the medical indications for these agents, and the experimental data supporting an important role of the renin-angiotensin system in the pathogenesis of intimal hyperplasia.

Influence of ramiprilat and losartan on ischemia reperfusion injury in rat hearts

Hypothesis/introduction: Our aim was to investigate whether a non-hypotensive dose of ramiprilat and losartan has myocardial protective effects during myocardial ischemia/reperfusion in vivo.

Materials and methods: Three groups of rats were given 10 mg/kg per day of losartan for one (L-1W), four (L-4W) or 10 (L-10W) weeks. Another three groups were given 50 µg/kg per day of ramiprilat for one (R-1W), four (R-4W) or 10 (R-10W) weeks. The animals underwent 30 min of left anterior descending artery occlusion and subsequent reperfusion for 120 min.

Results: Myocardial infarct size (IS) was reduced in R-1W (28.4 ± 6.3%, p < 0.001), R-4W (27.8 ± 7.4, p < 0.001), L-4W (31.8 ± 6%, p < 0.05) and L-10W (25.3 ± 5.7, p < 0.001) groups compared with a saline group (48.3 ± 7.8%). A significant reduction in the number of ventricular ectopic beats (VEBs) was noted in groups R-1W (209 ± 41, p < 0.01), R-4W (176 ± 39, p < 0.01), L-4W (215 ± 52, p < 0.05) and L-10W (191 ± 61, p < 0.01 vs. saline 329 ± 48). The incidence of irreversible ventricular fibrillation (VF) and mortality were decreased significantly only in L-10W group.

There were no significant decreases in episodes of VT, the incidence of irreversible VF and mortality in all of the groups treated with ramiprilat.

Conclusion: These data indicate that losartan and ramiprilat protect the heart against ischemia/reperfusion injury independently of their hemodynamic effects but in a time-dependent manner.

Prediction of off-target effects on angiotensin-converting enzyme 2

The authors describe a structure-based strategy to identify therapeutically beneficial off-target effects by screening a chemical library of Food and Drug Administration (FDA)-approved small-molecule drugs matching pharmacophores defined for specific target proteins. They applied this strategy to angiotensin-converting enzyme 2 (ACE2), an enzyme that generates vasodilatory peptides and promotes protection from hypertension-associated cardiovascular disease. The conformation-based structural selection method by molecular docking using DOCK allowed them to identify a series of FDA-approved drugs that enhance catalytic efficiency of ACE2 in vitro. These data demonstrate that libraries of approved drugs can be rapidly screened to identify potential side effects due to interactions with specific proteins other than the intended targets.

Alternative pathways for angiotensin II generation in the cardiovascular system

The classical renin-angiotensin system (RAS) consists of enzymes and peptides that regulate blood pressure and electrolyte and fluid homeostasis. Angiotensin II (Ang II) is one of the most important and extensively studied components of the RAS. The beneficial effects of angiotensin converting enzyme (ACE) inhibitors in the treatment of hypertension and heart failure, among other diseases, are well known. However, it has been reported that patients chronically treated with effective doses of these inhibitors do not show suppression of Ang II formation, suggesting the involvement of pathways alternative to ACE in the generation of Ang II. Moreover, the finding that the concentration of Ang II is preserved in the kidney, heart and lungs of mice with an ACE deletion indicates the important role of alternative pathways under basal conditions to maintain the levels of Ang II. Our group has characterized the serine protease elastase-2 as an alternative pathway for Ang II generation from Ang I in rats. A role for elastase-2 in the cardiovascular system was suggested by studies performed in heart and conductance and resistance vessels of normotensive and spontaneously hypertensive rats. This mini-review will highlight the pharmacological aspects of the RAS, emphasizing the role of elastase-2, an alternative pathway for Ang II generation.

Efficacy of ACE inhibitors in chronic heart failure with preserved ejection fraction--a meta analysis of 7 prospective clinical studies

BACKGROUND

The effect of ACE inhibitors on the prognosis of chronic heart failure patients with preserved left ventricular ejection fraction remains controversial.

AIMS

To assess the impact of ACE inhibitors on the prognosis of chronic heart failure patients with preserved left ventricular ejection fraction.

METHODS AND RESULTS

Seven prospective studies evaluating the effect of ACE inhibitors compared to placebo or other classes of drugs, such as monotherapy or first-line therapy, on the prognosis of chronic heart failure patients with preserved left ventricular ejection fraction were included. A total of 2554 patients (mean age: 75.1 years, female: 58%) were recruited with an average follow up of 20.9 months. The primary etiology of heart failure with preserved ejection fraction was ischemic heart disease (33.7%), hypertension (69.1%) and diabetes mellitus (25.8%). Our results demonstrated that ACE inhibitors significantly reduced all-cause mortality (odds ratio, OR = 0.52; 95% Confidence Interval (CI), 0.41 to 0.64; P<0.01). Furthermore, ACE inhibitors were able to reduce heart failure related rehospitalization or treatment over 20.9 months (p<0.05) in a subgroup of patients aged over 75 years. However, death due to worsening of heart failure, heart failure related rehospitalization and any-cause readmission were not affected (OR = 0.88; 95% CI: 0.66 to 1.17; P = 0.37 for death due to worsening of heart failure; OR = 0.81; 95% CI: 0.63 to 1.05; P = 0.11 for heart failure related rehospitalization and OR = 0.88; 95% CI: 0.68 to 1.14; P = 0.33 for any-cause readmission, respectively).

CONCLUSIONS

In patients with chronic heart failure with preserved ejection fraction, ACE inhibitors reduced all-cause mortality without affecting mortality due to heart failure and any-cause rehospitalization.

Valsartan-amlodipine-hydrochlorothiazide: the definitive fixed combination?

A significant proportion of patients with hypertension will need three or more antihypertensive agents to achieve blood pressure goals, particularly those at higher risk. On the other hand, fixed combinations provide an extra beneficial effect, as they improve medication adherence and, secondarily, the attainment of blood pressure goals during follow-up. Triple therapy is recommended in the treatment of hypertension in those patients not adequately controlled with two antihypertensive drugs. In this context, guidelines recommend the combination of a renin-angiotensin system inhibitor, a calcium channel blocker and a diuretic. The triple fixed combination of valsartan-amlodipine-hydrochlorothiazide has been shown to be an effective and safe therapy for treating hypertension and seems a logical approach for those patients uncontrolled with two antihypertensive agents as well as in those patients already treated with three drugs to improve treatment compliance. In this article, available evidence about the efficacy and tolerability of the triple fixed combined therapy valsartan-amlodipine-hydrochlorothiazide for the treatment of hypertension is updated.

Aliskiren in the management of hypertension

Angiotensin-converting enzyme inhibitors and angiotensin II type 1 receptor antagonists (angiotensin receptor blockers) have been shown to be effective drugs in the management of hypertension and to have beneficial effects along the cardiovascular continuum. However, due to compensatory mechanisms, both of these types of agent increase plasma renin activity, which has been reported to have deleterious effects on patient outcomes. Aliskiren is the first nonpeptide orally administered direct renin inhibitor available on the market. Reported data have shown that aliskiren effectively reduces BP alone or in combination with other antihypertensive agents, and has a good tolerability profile. Moreover, this agent reduces plasma renin activity, which in theory could have additional clinical benefits. However, clinical trials analyzing the effects of aliskiren on mortality are still ongoing.

Blocking the RAAS at different levels: an update on the use of the direct renin inhibitors alone and in combination

The renin–angiotensin–aldosterone system (RAAS), an important regulator of blood pressure and mediator of hypertension-related complications, is a prime target for cardiovascular drug therapy. Angiotensin-converting enzyme inhibitors (ACEIs) were the first drugs to be used to block the RAAS. Angiotensin II receptor blockers (ARBs) have also been shown to be equally effective for treatment. Although these drugs are highly effective and are widely used in the management of hypertension, current treatment regimens with ACEIs and ARBs are unable to completely suppress the RAAS. Combinations of ACEIs and ARBs have been shown to be superior than to either agent alone for some, but certainly not all, composite cardiovascular and kidney outcomes, but dual RAAS blockade with the combination of an ACEI and an ARB is sometimes associated with an increase in the risk for adverse events, primarily hyperkalemia and worsening renal function. The recent introduction of the direct renin inhibitor, aliskiren, has made available new combination strategies to obtain a more complete blockade of the RAAS with fewer adverse events. Renin system blockade with aliskiren and another RAAS agent has been, and still is, the subject of many large-scale clinical trials and furthermore, is already available in some countries as a fixed combination.

Do we need more than just powerful blood pressure reductions? New paradigms in end-organ protection

Antihypertensive therapy can lower the risk of cardiovascular morbidity and mortality. Yet, partly because of inadequate dosing, wrong pharmacological choices, and poor patient adherence, hypertension control remains suboptimal in the majority of hypertensive patients. Achieving greater blood pressure control requires a multifaceted approach that raises awareness of hypertension, uses effective therapies, and improves adherence. Particular classes of antihypertensive therapy have beneficial actions beyond blood pressure and studies have evaluated differences in cardiovascular protection among classes. The LIFE and HOPE studies showed between-class differences that may be due to effects other than blood pressure-lowering. In the ONTARGET study, telmisartan and ramipril provided similar cardiovascular protection but adherence was higher with telmisartan, which was better tolerated. This difference in compliance is likely to be important for long-term therapy. The selection of an agent for cardiovascular protection should depend on an appreciation of its composite properties, including any beneficial effects on tolerability and increased patient adherence, as these are likely to be advantageous for the long-term management of hypertension. This review examines the evidence that the effects beyond blood pressure provided by some antihypertensive agents can also lower the risk of cardiovascular, cerebrovascular, and renal events in patients with hypertension.

Reduction of blood pressure in patients with treatment-resistant hypertension

BACKGROUND

Resistant hypertension is a common clinical problem, and patients with resistant hypertension have increased cardiovascular risk. It is a subset of the hypertensive population that is little studied and poorly characterized.

OBJECTIVE

The purpose of this review is to discuss resistant hypertension, its recognition and diagnostic workup and management, and to present current data about the disease from the latest research.

METHODS

We define resistant hypertension and differentiate it from pseudoresistance. We identify diagnostic tests that may be done on patients with resistant hypertension. Last, we discuss therapeutic approaches to resistant hypertension, focusing on pharmacological treatment, and present an algorithm that may be used by the clinician in treating a patient with resistant hypertension.

CONCLUSION

Resistant hypertension is a significant clinical problem commonly encountered by clinicians. Patients with resistant hypertension have increased cardiovascular risk. In evaluating for resistant hypertension, it is important to recognize elements that contribute to pseudoresistance to treatment. Secondary causes of hypertension are common in patients with resistant hypertension and should be included in the diagnostic workup. Pharmacological treatment for resistant hypertension entails choosing medications with complementary mechanisms of action, optimizing diuretic use, and considering the use of mineralocorticoid antagonists as an add-on agent to the antihypertensive regimen.

Dual blockade of the renin-angiotensin-aldosterone system: beyond the ACE inhibitor and angiotensin-II receptor blocker combination

The renin-angiotensin-aldosterone system (RAAS), an important regulator of blood pressure as well as fluid and electrolyte balance, plays an important role in the pathophysiology of cardiovascular and kidney diseases. Blockade of the RAAS with angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin-II (ANG-II) receptor blockers (ARBs) lowers blood pressure, decreases morbidity and mortality in patients with chronic heart failure, and decreases proteinuria and the rate of decline in renal function in patients with chronic kidney disease. Although these drugs are highly effective and are widely used in the management of cardiovascular and kidney diseases, current treatment regimens with ACEIs and ARBs may not completely suppress the RAAS. Combinations of ACEIs and ARBs have been shown to be superior to either agent alone for some, but certainly not all, composite cardiovascular and kidney outcomes. With the growing appreciation of the role of aldosterone in the pathogenesis of cardiorenal diseases and the recent approval of the direct renin inhibitor (DRI), aliskiren, additional combination strategies have emerged that may offer novel ways to more fully suppress the RAAS. This review examines what is presently known about ACEI/ARB combination therapy and explores alternative combination strategies that include DRIs and mineralocorticoid receptor blockers (MRBs).

Comparison of the effects of candesartan cilexetil and enalapril maleate on right ventricular myocardial remodeling in dogs with experimentally induced pulmonary stenosis

OBJECTIVE

To compare the effects of candesartan cilexetil and enalapril maleate on right ventricular myocardial remodeling in dogs with experimentally induced pulmonary stenosis.

ANIMALS

24 Beagles.

PROCEDURES

18 dogs underwent pulmonary arterial banding (PAB) to induce right ventricular pressure overload, and 6 healthy dogs underwent sham operations (thoracotomy only [sham-operated group]). Dogs that underwent PAB were allocated to receive 1 of 3 treatments (6 dogs/group): candesartan (1 mg/kg, PO, q 24 h [PABC group]), enalapril (0.5 mg/kg, PO, q 24 h [PABE group]), or no treatment (PABNT group). Administration of treatments was commenced the day prior to surgery; control dogs received no cardiac medications. Sixty days after surgery, right ventricular wall thickness was assessed echocardiographically and plasma renin activity, angiotensin-converting enzyme activity, and angiotensin I and II concentrations were assessed; all dogs were euthanatized, and collagenous fiber area, cardiomyocyte diameter, and tissue angiotensin-converting enzyme and chymase-like activities in the right ventricle were evaluated.

RESULTS

After 60 days of treatment, right ventricular wall thickness, cardiomyocyte diameter, and collagenous fiber area in the PABNT and PABE groups were significantly increased, compared with values in the PABC and sham-operated groups. Chymase-like activity was markedly greater in the PABE group than in other groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that treatment with candesartan but not enalapril effectively prevented myocardial remodeling in dogs with experimentally induced subacute right ventricular pressure overload.